Organic matters have effective functions on physical, chemical and fertility properties of soils. This study was conducted in order to evaluate the effects of organic matters and Slag on available phosphorous, carbon dioxide volatilization, humus substances content, plant dry yield and total P. This Experiment was performed in four stages. The first stage consists of 16 weeks' incubation period of treated Entisol, Mollisol and Inceptisol with Municipal Compost (MC), Decomposed Farm Yard (DFYM) and Rice Straw (RS) which added to these soils in proportion of 1% organic carbon. Slag also added to soils in proportion of 1% . Phosphorus was extracted at the end of 1, 2, 4, 8, 12 and 16 weeks after incubation by Olsen method. At the other stage, Humus substances were measured at the end of sixteenth week. At the 3rd stage beside above mentioned stages, carbon dioxide volatilization was measured in described treatments on interval periods within 2 months. Finally, corn (Zea mays. L) was cropped in treated Inceptisol by organic matters. Results of first stage showed: 1.Kinds of additive materials had a significant effect on available P 2. Types of soil affected on available P 3.Maximum available P observed in first week= 65.16mgPKg-1, Total Week's extractions P determined a reductive trend. Results of extraction and fractionation of humus substances indicated that DFYM treatment, Mollisol and DFYM+Mollisol had maximum contents of fulvic acid and Humic acid. Their minimum quantities were observed in slag, Entisol and Slag+Entisol treatments. Results of carbon dioxide volatilization experiential consist of: 1. different additive materials were affected on CO2 volatilization significantly; as SR and Slag had maximum and minimum contents respectively . 2. Soil type had considerable effects. 3. Maximum amounts of CO2 volatilization were occurred during fourth day after applying in all treatments and gradually CO2 volatilization reduced.